1. Field of the Invention
The present invention relates to semiconductor integrated circuit apparatuses and radio-frequency power amplifier modules. In particular, the present invention relates to a technology effectively applied to a semiconductor integrated circuit apparatus and a radio-frequency power amplifier module that include detection circuits of transmission power and that support multiple communication methods.
2. Description of the Related Art
For example, Japanese Unexamined Patent Application Publication No. 2006-324878 discloses a radio communication apparatus including different power amplifier circuits for different communication methods (for example, Global System for Mobile communications (GSM) (registered trademark) and Universal Mobile Telecommunications System (UMTS)). Japanese Unexamined Patent Application Publication No. 2001-211125 discloses a detection circuit that appropriately adjusts the range of a thermal detection circuit having a narrow dynamic range by using the result of detection by a Received Signal Strength Indicator (RSSI) detection circuit having a wide dynamic range. Japanese Unexamined Patent Application Publication No. 2009-284034 discloses a configuration including a first detector that detects output power from a final-stage amplifier circuit and a second detector that detects source-drain voltage of the final-stage amplifier circuit. In such a configuration, input power from an upstream variable gain amplifier is controlled in accordance with the result of addition of detected signals from the respective detectors.
Multi-mode (for example, multiple modes including GSM and Wideband Code Division Multiple Access (W-CDMA)) and multi-band (multiple frequency bands) radio communication terminals (cellular phones) that support multiple communication methods and multiple frequency bands are in widespread use in recent years. The communication methods include GSM, Enhanced Data Rates for GSM Evolution (EDGE), UMTS or W-CDMA, and Long Term Evolution (LTE). EDGE is a method resulting from extension of GSM, and a modulation method resulting from modification of 8-phase shift keying (8PSK) is used in EDGE, in addition to a Gaussian filtered Minimum Shift Keying (GMSK) modulation method. Such a radio communication terminal is required to be capable of stable communication against reduction in size and change in external environment.
For example, a radio-frequency power amplifier module used in a transmission system of the radio communication terminal is required to have characteristics for stably transmitting amplified output power having a value within a communication standard even in a state in which the change in external environment (a change in temperature, a variation in battery voltage, impedance mismatching between an antenna and the space, etc.) occurs. In order to suppress the variation in the output power, the power amplifier module usually includes a radio-frequency power amplifier (a power amplifier circuit) (PA) and a detection circuit that detects the magnitude of an output power signal (Pout) of the power amplifier circuit (PA). The detection circuit includes, for example, a directional coupler that generates a detected power signal (Pdet) using electromagnetic field coupling with Pout and a power detection circuit that generates a detected voltage signal (Vdet) corresponding to the magnitude of Pdet.
A review by the inventor of the above-described modules and methods determined the following. In the GSM mode, a feedback control method is usually used to control the output power from the power amplifier circuit (PA). Specifically, for example, an error amplifier detects the difference between a target value (a power instruction signal VRAMP) of the output power signal (Pout) of the power amplifier circuit (PA) and the detected voltage signal (Vdet) of Pout by the detection circuit, and the gain of PA is subjected to the feedback control so that the difference comes close to zero. If the detection sensitivity of the power detection circuit is low (that is, the relationship between Pdet (Pout) and Vdet is inappropriate), the controllability of Pout with VRAMP is reduced, thereby possibly increasing the variation in Pout. It is desirable in the GSM mode to use the detection method enabling high sensitive power detection in both a low power region and a high power region because the wide-range power control is required in the GSM mode.
In contrast, in the EDGE mode, the feedback control method described above is not usually used. The detected voltage signal (Vdet) is output from a terminal outside the module and is used for the gain control in a variable gain amplifier circuit positioned upstream of PA outside the module. Such a method is used in the EDGE mode because envelope line variation occurs, unlike the GSM mode (GMSK modulation) in which constant envelope line modulation is used, and linear amplification is required in conjunction with the envelope line variation. In this method, power measurement of Pout is alternatively performed via Vdet output from the terminal outside the module and the gain control of the variable gain amplifier circuit (that is, control of an input power signal (Pin) of PA) is performed on the basis of the result of the measurement. In the control, it is necessary to know in advance the detection sensitivity of the power detection circuit (the relationship between Pdet (Pout) and Vdet). If the relationship becomes complicated, the controllability of Pin is reduced, thereby possibly increasing the variation in Pout. Accordingly, it is desirable in the EDGE mode to use a detection method in which the relationship between Pdet (Pout) and Vdet is represented by a simple function in the power detection circuit.
The relationship between Pdet (Pout) and Vdet may be practically varied in accordance with the variation in the process, various variations in the environment, or the like. Accordingly, in order to correct the variation, it is necessary to perform calibration in advance. In the calibration, the actual measurement is performed at multiple predetermined calibration points and an approximate expression between Pdet (Pout) and Vdet is calculated on the basis of the result of the measurement. If the relationship between Pdet (Pout) and Vdet is complicated, the number of the calibration points is possibly increased and/or the precision of the approximate expression is possibly reduced. Accordingly, also in terms of this point, it is desirable to use a detection method in which the relationship between Pdet (Pout) and Vdet is represented by a simple function in the power detection circuit.
As described above, in the suppression of the variation in the output power signal (Pout), there are cases in which different detection methods are required to be used for different modes because the desired detection method of the power detection circuit is varied depending the communication method (mode). However, since different power detection circuits are usually separately mounted for different detection methods in such cases, the radio communication terminal is possibly increased in size, in addition to the increase in the circuit area.